linux-kernel - Re: [PATCH] hwmon: (dme1737): Add missing null check on return from platform_get

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Date:   Fri, 9 Apr 2021 16:08:37 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Colin King <colin.king@...onical.com>
Cc:     Juerg Haefliger <juergh@...il.com>,
        Jean Delvare <jdelvare@...e.com>,
        "Mark M . Hoffman" <mhoffman@...htlink.com>,
        linux-hwmon@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH]  hwmon: (dme1737): Add missing null check on return from
 platform_get_resource

On Tue, Apr 06, 2021 at 07:54:58PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The call to platform_get_resource can potentially return a NULL pointer
> on failure, so add this check and return -EINVAL if it fails.
> 
> Addresses-Coverity: ("Dereference null return")
> Fixes: e95c237d78c0 ("hwmon: (dme1737) Add sch311x support")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Not really sure what to do with this; it is a false positive.
The resource is always set by the instantiating code (in the same
driver). Adding an error check just to make coverity happy seems
like a waste. Maybe we should introduce the equivalent of
devm_ioremap_resource() for IORESOURCE_IO.

Guenter

> ---
>  drivers/hwmon/dme1737.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwmon/dme1737.c b/drivers/hwmon/dme1737.c
> index c1e4cfb40c3d..a2157872e126 100644
> --- a/drivers/hwmon/dme1737.c
> +++ b/drivers/hwmon/dme1737.c
> @@ -2633,6 +2633,8 @@ static int dme1737_isa_probe(struct platform_device *pdev)
>  	int err;
>  
>  	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
> +	if (!res)
> +		return -EINVAL;
>  	if (!devm_request_region(dev, res->start, DME1737_EXTENT, "dme1737")) {
>  		dev_err(dev, "Failed to request region 0x%04x-0x%04x.\n",
>  			(unsigned short)res->start,